Have you ever felt like your wife was hiding something from you? Legendary Chinese scholar Xu Xian (许仙) had that feeling once, too. And it turned out he was right. Xu Xian’s wife was hiding the fact that she was actually a snake demon.

At least, that’s the basic premise of the legend of the white snake, one of China’s most popular and pervasive myths. It’s an old one too; the first printed version of the story appeared during the Ming Dynasty (1368-1644) but the tale had been passed down orally long before that.

There are dozens, probably hundreds of variations of the story, which has also changed significantly over time. At first, the snake-woman was portrayed as evil, and the tale was a horror story. But over time, it gradually became a love story that’s either tragic or triumphant, depending on who is doing the telling. Here’s the basic gist:

Once upon a time, there was a white snake demon named Bai Suzhen (白素贞). She lived in the realm of demons, but aspired to become more powerful. Some say she wanted to become a goddess, others that she dreamed of using her powers to help people. But either way, she came to the human world and, to blend in, took on the form of a beautiful woman.

While there, she met a green snake demon named Xiao Qing (小青) who was causing trouble. After some initial scuffles, the two became close friends and traveled the world together in human form. It was atHangzhou’sWestern Lakethat they met the renowned Chinese scholar Xu Xian. White Snake Bai fell head over heels for the human, and used her magical wiles to set up more opportunities for them to meet again and again, until they finally married.

It was not meant to be, however. An itinerant sorcerer named Fa Hai (法海) could see Bai and Qing for what they really were, and—dedicated to destroying all demons—told Xu Xian the truth. Terrified, Xu Xian urged Fa Hai to attack, and Bai ended up trapped in the Hangzhou’s Thunder Pagoda (雷峰塔 Léifēng Tǎ). Xu Xian, finished with the material world, became a monk.

Now, originally, this was a horror story, and it ended there. Bai is, after all, a demon. But people tend to like happy stories more than they like sad ones, and romantic stories more than horror stories. So the tale of the White Snake Lady changed. Bai, once the tale’s villain, became a heroine fighting for love against all odds. And Fa Hai, once the hero, became the closed-minded villain determined to keep humans and demons apart. (Even if they were the good, lovable kind of demons.)

In more recent tellings, Bai is not imprisoned by Fa Hai after her marriage with Xu Xian, and Xu Xian is not aware his wife is a snake demon. They open a medicine shop together and become widely known for giving away free herbs to people who can’t afford to pay.

One year during the Dragon Boat Festival, while Bai is pregnant with their first son, her husband brews up a special surprise recommended by Fa Hai: wine infused with herbs that will expel all demons. Unable to think of a convincing excuse, Bai drinks the wine and immediately turns back into a snake. Her husband, shocked beyond belief, ups and dies. Bai returns to human form, obtains some sacredKunlunMountainherbs, and brings her husband back to life.

Here, the stories really diverge. In some versions, Bai is able to convince him that the snake was just a dream, and they live happily ever after with their son. Sometimes Bai admits that she is a snake demon, but her husband accepts this and the story ends with the two of them caring for their young son.

But often it’s darker. One version has Fa Hai locking Xu Xian away inJinshanTemplefor his own protection. Bai furiously destroys the temple, violating the laws of Heaven, and is doomed to eternal imprisonment in the Thunder Pagoda. Sometimes a magical hat imprisons Bai in Thunder Pagoda. Sometimes Xiao Qing, the green snake demon, comes to her aid. And so often, the story ends with Bai, her husband, and their son finally reunited.

It’s changed greatly over the years, but the story continues to enjoy popularity to this day, spawning books, operas, movies, modern dances and multiple television series. The White Snake story most recently graced the small screen in 2006, but every Chinese TV geek knows that the 1993 adaptation, “新白娘子传奇” (Xīn bái niángzǐ chuánqí, Legend of White Snake) is the best modern adaptation.